Who is believed regarding the age of the perpetrator at the time of the offense (child vs. adult)?

Primary text

When the perpetrator and the victim's guardian disagree on the perpetrator's age at the time of the offense, and the perpetrator claims to have been a child (*sabi*) while the guardian claims he was an adult (*baligh*), the perpetrator's statement is accepted along with his oath, provided that the claim is plausible. This is based on the principle that the default state is minority, ensuring the acquittal of his liability from retribution (*qisas*).